Low-Power and Lossy Networks (LLNs), e.g., sensor networks, have a myriad of applications, such as Smart Grid and Smart Cities. Various challenges are presented with LLNs, such as lossy links, low bandwidth, battery operation, low memory and/or processing capability of a device, etc. Changing environmental conditions may also affect device communications. For example, physical obstructions (e.g., changes in the foliage density of nearby trees, the opening and closing of doors, etc.), changes in interference (e.g., from other wireless networks or devices), propagation characteristics of the media (e.g., temperature or humidity changes, etc.), and the like, also present unique challenges to LLNs.
The Institute of Electrical and Electronics Engineers (IEEE) 802.11ah standard represents one way to implement an LLN. A key feature of 802.11ah is sub-Gigahertz communications to extend traditional WiFi coverage. 802.11ah also makes use of relay access points that exchange frames with a networking station, to further extend coverage.
While standards such as 802.11ah provide a mechanism to implement certain types of LLNs, such mechanisms may not be suitable for other forms of LLNs. Notably, many industrial networks require very precise timing and reliability (e.g., strictly bounded latency, etc.). For example, a control signal for a stamping machine on an assembly line must reach the stamping machine at a precise time, to ensure that the next stamping action is in sync with the next object to be stamped on the assembly line. However, in 802.11ah and similar mechanisms, devices form a single association with a relay or access point, creating a single point of failure. Further, these mechanisms use a repeat process that rely on automatic repeat requests (ARQs), which may prevent the original message from reaching its destination in time.